Due to the flexible and soft nature of the flexible printed circuit board (FPC), it is ideally suited for scenes where parts of a phone are often repetitively bent. Taking a flexible circuit board as an example, copper foil layers, adhesive layers, and cover layers are respectively disposed on both sides of the dielectric layer. The two copper foil layers are respectively plated on the upper and lower sides of the dielectric layer, and each cover layer covers over the corresponding copper foil layer via the respective adhesive layer.
On flexible circuit boards, certain special areas need to be particularly flexible and easy to bend repeatedly. In the current design of flexible circuit boards, single-sided traces are generally adopted, i.e., the copper skin of the remaining layers is cut off, and the cover layer covering the surface of the copper skin is also removed, so that this local area is thin and easy to bend in use. The copper foil layer, the adhesive layer, and the cover layer on the dielectric layer are cut off to form the bending area of the flexible circuit board. This process is also called “window processing” to reduce the thickness of the bending area of the flexible circuit board to make it more flexible and easy to bend.